Gr 4-6-- In this fourth installment in the popular series, hypnotist and time-traveler Molly Moon, 11, pursues her twin brother, Micky, who, until recently--due to the paradoxes of time travel--she never knew she had. She also learns that she can read people's (and animals') thoughts. Molly, her beloved pug, and her friend Rocky travel back in time, to the moments just after the twins had been born. A mysterious time-traveling character, disguised as a doctor, sneaks out of the hospital with the baby boy, and 11-year-old Molly and Rocky and Petula pursue them hundreds of years into the future to a kingdom atop a now-desertlike Mont Blanc. This kingdom is ruled by Princess Fang, a bossy, bratty, but highly intelligent six-year-old who uses Micky's hypnotic powers to turn everyone into her slave, with the goal of hypnotizing international leaders and one day ruling the world. Micky doesn't believe that Molly is his sister and won't help her escape. Of course, Molly Moon refuses to be kept a prisoner long. The weight of details and characters from the previous books, added to lots of new details and characters here, slows the pace of this volume, and it drags. This big, puttering tale will interest only fans of the series.--Walter Minkel, New York Public Library[Page 115]. Copyright 2008 Reed Business Information.